Weightlessness Demonstration

Standards Addressed

MEGOSE ES5 Describe and explain common observations of the day and night skies.
MEGOSE ES12 Explain how technology and scientific inquiry have helped us learn about the universe.

Quick Summary of Lesson

This lesson demonstrates that free-fall eliminates the local effects of gravity.

Materials

Styrofoam or paper coffee cup
Pencil or other pointed object
Water
Bucket or other catch basin

Procedure

1. Punch a small hole in the side of the cup near its bottom.

2. Hold your thumb over the hole as you fill the cup with water. Ask students what will happen if you remove your thumb.

3. Remove your thumb and let the water stream out into the catch basin on the floor.

4. Again seal the hole with your thumb and refill the cup. Ask students if the water will stream out of the hole if you drop the cup.

5. Drop the filled cup in to the catch basin. The demonstration is more effective when you hold the cup high before dropping it.

6. Lead students in discussion based on Notes to Teacher below.

Notes to the Teacher

Earth-orbiting spacecraft experience a condition described as weightlessness. The spacecraft is in a state of free-fall as it orbits. If the spacecraft has astronauts on board, the astronauts are able to move about with ease because they too are in a state of free-fall. In other words, everything in their immediate world is falling together. This creates the weightless condition. Crew members and all the other contents of the spacecraft seemingly float through the air.

On Earth, momentary weightlessness can be achieved in a number of ways. Some amusement parks achieve a second or two of weightlessness in certain wild high-tech rides. NASA achieves about 30 seconds of weightlessness with a special airplane fondly termed the Vomit Comet. High above Earth, the plane begins a long arc-like dive downward at a speed equal to the acceleration of a falling object. After 30 seconds, the plane pulls out of the dive and climbs back to the high altitude to begin another weightless cycle.

The falling cup for a moment demonstrates weightlessness. When the cup is stationary, water freely pours out of the cup. If the cup falls, the water remains inside the cup for the entire fall. Even though the water remains inside, it is still attracted to Earth by gravity and ends up in the same place that the water from the first experiment did.

The demonstration works best when students are asked to predict what will happen when the cup is dropped. Will the water continue to pour out the holes as the cup falls? If your school has videotape equipment, you may wish to videotape the demonstration and then use the slow motion on the plackback machine to replay the action.